1. Field of the Invention
This invention is concerned with improving the pour characteristics of residual fuel oils by incorporating therein certain low molecular weight highly-branched polymers of alpha-olefins. More particularly, the invention relates to improved residual fuel oils containing an effective pour depressant amount of a polymer of a normal (i.e., straight chain) alpha-olefin of from 10 to 16 carbon atoms. In another aspect this invention relates to the low-molecular weight, highly branched alpha-olefin copolymer compositions.
2. Description of the Prior Art
As is well known, residual fuel oils contain quantities of wax and asphaltic compounds which render them viscous and interfere with practical use of such oils. In particular, serious problems are encountered in pumping residual fuel oils to burners in pipe lines, etc. and in making them flow at low temperatures. Other factors to be reckoned with are that these oils behave as non-Newtonian liquids at low temperatures and they exhibit variable solidifying temperature and peculiar hysteresis phenomena, all of which make for difficulties in equipment design.
One approach in making these oils easier to handle has been to subject them to fairly lengthy dewaxing procedures.
Another approach which has been used to bring the viscosity of residual fuel oils to suitable level has been to dilute or "cut" them with a major amount of lighter distillate oils but this is an expensive procedure because of the considerably higher cost of the distillate oils relative to the residual oils.
A number of additives have been suggested and tried with success in lubricating oils and in so-called middle distillates in order to tie in the wax therein and improve flow at low temperatures. Such additives consist either of compounds formed by alkylating benzene or naphthalene derivatives or of copolymers of ethylene-vinyl fatty acid ester of a molecular weight up to 60,000 and containing from 15 to 25% by weight of the vinyl saturated aliphatic monocarboxylic acid ester.
The additive mentioned previously being solids, all suffer from one or more disadvantages. For example, they are difficult to dissolve in the residual fuels and generally they must be added with mixing as a solution in a suitable solvent such as toluene, etc. to the heated residual fuel.
One of the main objects of this invention is to provide oil-soluble copolymer pour depressants which are liquids and therefore easily incorporated into residual fuels.
Another object of the present invention is to improve the pour point characteristics of residual oils without using elaborate dewaxing procedures.
An equally important object of this invention is to provide heating oils and fuel oils having improved pour point characteristics by incorporating therein a small amount of certain highly-branched alpha-olefin copolymers.